Man made air pollution is a well-known fact. Reducing unnecessary pollution is accepted today to be important. A large amount of air pollution is generated by man made devices for burning fossile energy. Many attempts have been recently made to clean up the exhaust and/or flue gases leaving said devices.
The primary object of the hereinafter described invention is to conduct the combustion process so as to dramatically reduce at least some components of its final residual products, as, for example, partially burnt hydrocarbons and nitrogen oxides. Furthermore, an extraordinarily cheap and hence cost-benefit optimized method of controlling said combustion process is aimed for and described hereinafter.
Although the claims are basically self-explanatory for those skilled in the art, a short description is provided hereinafter in combination with the description of FIG. 1 showing the flow chart of the preferred steps in a schematic manner.
If a predetermined amount of power is demanded for, let us assume X KW, designated by Q.sub.1, then, due to efficiency losses, as is well-known, a larger amount of power=X times total efficiency, designated by Q.sub.2, must be generated.
In the case of a thermal power generating device, correspondingly combustible material, hereinafter called fuel, must be introduced into a particular zone where combustion takes place. Essentially simultaneously a corresponding amount of oxygen, usually contained in ambient air must also be carried towards said zone. The aforesaid zone quoted Z is usually arranged in a predetermined combustion space wherein combustion hereinafter referred to is to take place.
Up to now, combustion of burnable products or fuel will conform to natural laws whereby an initially smaller rate of heat release, hereinafter call ROHR, is followed upon a time axis by a higher ROHR, and, towards the end of the oxidation process, when already a majority part of the obtainable heat has been released out of a given quantum of burnable components, said ROHR might become smaller than at the time, where only about 60% of heat has been generated.
It has been found by the applicant that a controlled ROHR efficiently contributes to improve combustion and simultaneously dramatically reduces undesired pollution normally generated by conventional combustion processes with exhaust gases being permitted to escape in the usual manner through a stack.
It has also been found by the applicant that the most efficient method to control the ROHR is to recirculate exhaust gases back into the oxygen or oxygen containing air destined for the combustion, hereinafter referred to as EGR for exhaust gas recirculation.
It therefore remains to be determined for a desired ROHR, to measure the effective ROHR and then to control said ROHR in a desired manner, preferably in combination with a closed loop control means.
The measurement of a ROHR is preferably realized by at least one, preferably temperature related, measurement in a first combustion zone quoted A, where combustion, respectively oxidation, takes place. A more efficient method is achievable by measuring a second temperature related value in a second combustion zone quoted B, preferably following said first zone in respect of the heat released already by the oxidizing components. The first and second temperature related values, which will be referred to in greater detail hereinafter, allow for more accurate determination of said ROHR which preferably has to be determined at a given time and at the then prevailing and/or given operating conditions of such thermal power release.
The improved method to be revealed herein has been applied to small scale thermal power generators having a controllable power output between 300 to 1000 KW. The obtained improvements have been:
ca. 50% reduction of the usual losses encountered with state of the art heat generating; PA1 ca. 80% reduction in unburnt hydrocarbons; PA1 ca. 50% reduction in CO emissions; PA1 ca. 60% reduction of NO.sub.x emissions; PA1 reduced control and maintenance costs and PA1 improved cost-benefit-emission ratio.
Further improvements are considered possible by those skilled in the art.
A so-called retrofit onto existing power plants is extremely cheap to achieve.
An apparatus according to the invention is easily produced upon the revealed teaching by those skilled in the art.
The invention will be better understood and further objects and advantages thereof will become more apparent from the ensuing detailed description of a preferred embodiment taken in conjunction with the drawings.